Effectiveness of orthodontic treatment with functional appliances on mandibular growth in the short term

Establishing better biological models to understand occlusion. I: TM joint anatomic relationships

Belief in and rejection of a relationship of occlusion and temporomandibular joint (TMJ) condyle-fossa position with normal and abnormal function are still contentious issues. Clinical opinions can be strong, but support in most published data (mostly univariate) is problematic. Distribution overlap, low sensitivity and specificity are a common basis to reject any useful prediction value. Notwithstanding, a relationship of form with function is a basic tenet of biology. These are multifactor problems, but the questions mostly have not been analysed as such. This review moves the question forward by focusing on TM joint anatomic organisation as the multifactor system it is expected to be in a closed system like a synovial joint. Multifactor analysis allows the data to speak for itself and reduces bias. Classification tree analysis revealed useful prediction values and usable clinical models which are illustrated, backed up by stepwise logistic regression. Explained variance, R(2), predicting normals from pooled TMJ patients was 32·6%, sensitivity 67·9%, specificity 85·7%; 37% versus disc displacement with reduction; and 28·8% versus disc displacement without reduction. Significant osseous organisational differences between TM joints with clicking and locking suggest that this is not necessarily a single disease continuum. However, a subset of joints with clicking contained characteristics of joints with locking that might contribute to symptom progression versus resistance. Moderately strong models confirm there is a relationship between TMJ osseous organisation and function, but it should not be overstated. More than one model of normals and of TM derangement organisation is revealed. The implications to clinical decision-making are discussed.

Long-term skeletal and dental effects and treatment timing for functional appliances in Class II malocclusion

OBJECTIVE

To analyze the long-term skeletal and dentoalveolar effects and to evaluate treatment timing of Class II treatment with functional appliances followed by fixed appliances.

MATERIALS AND METHODS

A group of 40 patients (22 females and 18 males) with Class II malocclusion consecutively treated either with a Bionator or an Activator followed by fixed appliances was compared with a control group of 20 subjects (9 females and 11 males) with untreated Class II malocclusion. Lateral cephalograms were available at the start of treatment (mean age 10 years), end of treatment with functional appliances (mean age 12 years), and long-term observation (mean age 18.6 years). The treated sample also was divided into two groups according to skeletal maturity. The early-treatment group was composed of 20 subjects (12 females and 8 males) treated before puberty, while the late-treatment group included 20 subjects (10 females and 10 males) treated at puberty. Statistical comparisons were performed with analysis of variance followed by Tukey's post hoc tests.

RESULTS

Significant long-term mandibular changes (Co-Gn) in the treated group (3.6 mm over the controls) were associated with improvements in the skeletal sagittal intermaxillary relationship, overjet, and molar relationship (∼3.0-3.5 mm). Treatment during the pubertal peak was able to produce significantly greater increases in total mandibular length (4.3 mm) and mandibular ramus height (3.1 mm) associated with a significant advancement of the bony chin (3.9 mm) when compared with treatment before puberty.

CONCLUSION

Treatment of Class II malocclusion with functional appliances appears to be more effective at puberty.

The ability of orthodontists and laypeople to discriminate mandibular stepwise advancements in a Class II retrognathic mandible

OBJECTIVES

This study analysed the ability of orthodontists and laypeople to discriminate mandibular stepwise advancements.

MATERIALS AND METHODS

Four pictures (in duplicate) were taken of a male patient with Class II malocclusion and mandibular deficiency with the mandible positioned in habitual maximum intercuspation (HMI) and with stepwise advancements of 2mm, 4mm and 6mm. These images were examined by orthodontists (n=30) and laypeople (n=30). The Wilcoxon signed-rank test was used to evaluate intra-examiner agreement. Intra-examiner ability to discriminate stepwise mandibular advancements was examined by Friedman's test. A Mann-Whitney's test was carried out to analyse score difference between orthodontists and laypeople. Type I error (alpha) was set as 5% for all statistical tests.

RESULTS

We observed a satisfactory to excellent level of methodological reliability. While laypeople were able to notice mandibular advancements ≥4 mm (p<0.05), orthodontists were able to observe mandibular advancements ≥2 mm (p<0.05). The orthodontists were more critical than laypeople with regard to the facial profile evaluation when facial convexity increased (p<0.001), but no significant difference was observed when the sagittal maxillo-mandibular relationship approached normality (p<0.05).

CONCLUSIONS

Considering that the mean sagittal mandibular growth due to the use of functional orthopaedic appliances is reported in the literature as 2mm, it seems that laypeople may not able to discriminate this amount of change in facial-profile attractiveness.

Effectiveness of bionator therapy for Class II malocclusions: a comparative long-term study

OBJECTIVE

The goal of this retrospective study was to examine the effectiveness of isolated bionator therapy in Class II patients both longitudinally and over the long term. We aimed to determine whether skeletal and/or dentoalveolar reactions differ in relationship to the Angle Class (II, Division 1 vs. II, Division 2).

PATIENTS AND METHODS

A total of 50 juvenile patients with Class II malocclusion (♀ n = 26, ♂ n = 24) were included. A total of 24 patients presented an Angle Class II, Division 1 and 26 an Angle Class II, Division 2. We compared the patients' lateral cephalograms taken at the beginning of treatment (t1: 10.1 years), after active therapy (t2: 13.8 years), and at the end of retention (t3: 16.4 years) analyzing the following cephalometric parameters: SNA, SNB, ANB, ANB(ind), SNPog, Wits appraisal, U1-SN, U1-SpP, L1-MeGo, interincisal angle. Mean and standard deviations of each of the variables were calculated. Differences between t1-t2 and t2-t3 were tested for statistical significance. Changes in the variables were then analyzed biometrically for specific differences in terms of Angle Class (II, Division 1 vs. II, Division 2).

RESULTS

Between t1 and t2, SNB (p = 0.000) and SNPog (p = 0.000) increased significantly, as did ANB (p = 0.000), while the difference between ANB and ANB(ind) (p = 0.000) and Wits appraisal (p = 0.000) decreased significantly. The dentoalveolar variables U1-SN, U1-SpP, and the interincisal angle changed significantly in both groups. The inclination of the upper incisors was corrected by retrusion in the Class II, Division 1 and by protrusion in the Class II, Division 2 group. Only marginal changes in all variables between t2 and t3 were observed.

CONCLUSION

A significant skeletal effect (even in long-time stability) through bionator treatment could be confirmed in this study of Class II, Divisions 1 and 2 patients. The desired effect on the upper front teeth was realized, and there was no appreciable dentoalveolar compensation in the mandible.